1. Field of the Invention
The present invention relates to a musical tone waveform signal generating apparatus adapted for use in an electronic musical instrument, a music education system, an amusement tool or the like, and more particularly to a musical tone waveform signal generating apparatus designed to circulate a waveform signal for producing a musical tone waveform signal in response to a performance information applied thereto.
2. Description of the Prior Art
Japanese Patent Laid-Open Publication No. 63-40199 discloses a conventional musical tone waveform signal generating apparatus of this kind which includes an excitation circuit portion and a signal transmission portion, the former circuit portion having means for mixing a circulated waveform signal with an excitation control signal applied thereto from an external source of signals and a non-linear conversion circuit for non-linearly converting the mixed waveform signal into an output waveform signal to be generated as a musical tone waveform signal, and the latter circuit portion being arranged to feed back the output waveform signal to the excitation circuit portion with delay of a predetermined time thereby to obtain a resonance frequency corresponding to a pitch of the musical tone to be generated. In the musical tone waveform signal generating apparatus, the excitation circuit portion is desinged to correspond with the mouth-piece of a wind instrument, while the signal transmission circuit portion is designed to correspond with the resonance tube of the wind instrument so that the waveform signal circulated through the excitation and signal transmission circuit portions is generated as the musical tone waveform signal.
In the conventional apparatus described above, the non-linear conversion circuit is provided with only a single non-linear table for conversion of the mixed waveform signal. With such a single non-linear table, it is impossible to vary the non-linear characteristic of the mixed waveform signal at the excitation circuit portion. This means that the musical tone waveform signal is generated only in the form of a single kind of waveform signal. For this reason, the conventional apparatus is insufficient for use in an electronic musical instrument, a music education system, an amusement tool or the like.